Obama's grandmother, pictured with Obama when he was a college student, has died.

(CNN) - Barack Obama's grandmother, Madelyn Dunham, has died following a bout with cancer, Obama and his sister, Maya Soetoro-Ng, said Monday.

She was 86.

"She was the cornerstone of our family, and a woman of extraordinary accomplishment, strength, and humility," their statement said. "She was the person who encouraged and allowed us to take chances. She was proud of her grandchildren and great-grandchildren and left this world with the knowledge that her impact on all of us was meaningful and enduring. Our debt to her is beyond measure."

Obama and Soetoro-Ng asked that donations be made for the search for a cure for cancer in lieu of \ flowers. A small private ceremony will be held "at a later date."

The Democratic presidential candidate left the campaign trail on October 23 and flew to Honolulu, Hawaii, to spend the day with Dunham, whose health deteriorated after she suffered a broken hip.

His wife, Michelle Obama, filled in for him at events in Columbus and Akron, Ohio, on October 24.

Obama said in an interview taped for that day's "Good Morning America" that Dunham had been "inundated" with flowers and messages from strangers who read about her in Obama's 1995 book, "Dreams From My Father."

"Maybe she is getting a sense of long-deserved recognition toward the end of her life," he said.

The candidate resumed his campaign on October 25.

Obama has spoken about his grandmother often on the stump, talking about what an integral figure she was in his youth and how she struggled against the glass ceiling in her career. He and his family traveled to Hawaii in August to visit her.

"She's the one who put off buying a new car or a new dress for herself so that I could have a better life," he said in his acceptance speech at the Democratic National Convention. "She poured everything she had into me. And although she can no longer travel, I know that she's watching tonight, and that
tonight is her night as well."